Moisture exchange modules of the generic type are described in the prior art. For example, EP 1 338 852 shows a moisture exchange module of this type having a bundle of hollow fiber membranes, which have flowing around them a flow that is guided in countercurrent to the flow within the hollow fiber membranes.
Furthermore, DE 102 14 078 shows, in connection with the prior art, a moisture exchange module in which a moist gas stream is fed to the bundle of hollow fiber membranes centrally via a line provided with openings, with this moist gas stream, after it has flowed around the hollow fiber membranes, being collected in a collection space arranged around the bundle and discharged.
In both cases, the flow through parts of the bundle is poor, i.e. reached by only a small part of the volume of the gas stream, or even nonexistent. This will make the moisture exchange worse, and consequently relatively large modules are required to exchange a predetermined quantity of moisture between two gas streams. In particular, in the moisture exchange module described in DE 102 14 078, the cross section of the region of the hollow fiber membranes around which medium flows increases continuously in the direction of flow, so that fewer hollow fiber membranes are actively utilized in the region of the larger diameter at the bundle of hollow fiber membranes than in the interior of the bundle. This makes the moisture exchange module unnecessarily large for a predetermined exchange capacity.